In my prior U.S. Letters Pat. No. 4,874,641 are disclosed compositions for generating foam adapted to form an inexpensive, temporary barrier layer between a substrate, such as a layer of waste deposited in a landfill, and the atmosphere. As pointed out in the patent, such a barrier layer might serve to protect the atmosphere from deleterious materials which would escape from the substrate, such as odors and blowing trash from landfills, dust or noxious fumes from spills, and the like. As also pointed out in the patent, such a barrier layer might also serve to protect the substrate from adverse conditions in the atmosphere, as in protecting growing fruit, vegetables and plants from unseasonal frost. It might be added, in connection with the latter situation, that such a foam, particularly one prepared according to the present invention, might be used in the control of mine fires, specifically abandoned mine fires, where the foam can be pressure injected underground. In this application, the foam would serve four fundamental functions: (1) displacement of combustion air and gases which are products of combustion; (2) extinguishment of the actively burning zones; (3) heat removal from the surrounding strata; and (4) deposition of known chemical fire fighting ingredients (urea for instance) in order to minimize problems associated with reignition.
U.S. Pat. Nos. 4,421,788 and 4,519,338 relate to using a hardenable plastic foam to replace the daily compacted earth cover on a landfill. The foam employed according to these patents is prepared using a foaming agent and a liquid synthetic resin, such as a precondensate of urea and formaldehyde. U.S. Pat. No. 4,421,788 describes covering successive layers of refuse with foamed polyurethane, polyether or polyester-based resins.
Since the development of the foam composition of my prior patent, certain state governmental agencies have promulgated regulations governing sanitary landfills and the like with more stringent requirements. For example, there is a requirement that the sanitary landfill daily cover foam be six inches thick in addition to satisfying all other conventional requirements. Among the latter are the requirement that the cover be effective in sealing off of odors from, and in preventing insects from gaining access to, the waste, while being innocuous to the environment. The foam generated from the composition as disclosed in my prior patent was not stiff enough to "stack" six inches thick, especially on a slope and at low temperatures.
The foam-generating composition must be capable of being produced, transported, stored and handled as a concentrate in order to avoid the handling of large volumes of liquid which is mostly water. The concentrate, of course, is subjected to widely different atmospheric temperature conditions, including very low temperatures. Attempts at modifications of the prior foaming composition to meet the new technical and regulatory requirements led to other problems.
There are conflicts between soluble/insoluble characteristics of combinations of components in a foam-generating composition. Potassium soaps are generally much more soluble in water than sodium soaps, and higher molecular weight fatty acids, like palmitic and stearic, give more dense, more stable foams than lower molecular weight homologs. Yet, in order to obtain the stiffness and drain time performance (foam persistence), it is desirable to have the foam in the "insoluble" mode, while, on the other hand, in order to provide a foaming composition in the form of a concentrate, the materials should be in a "soluble" mode so that active ingredients are not precipitated and lost to the system. Solubility is also important to the ultimate foaming performance. It is generally accepted that soaps foam well in hot water, foam moderately in room temperature water and do not foam in cold water. Yet foams of the type to which the present invention is directed are generally applied under ambient temperature conditions ranging from below freezing, at the low end, to 90.degree.-100.degree. F. at the high end.